// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
/*
* Based on:
*
* Minimal BPF JIT image disassembler
*
* Disassembles BPF JIT compiler emitted opcodes back to asm insn's for
* debugging or verification purposes.
*
* Copyright 2013 Daniel Borkmann <[email protected]>
* Licensed under the GNU General Public License, version 2.0 (GPLv2)
*/
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <stdio.h>
#include <stdarg.h>
#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/stat.h>
#include <limits.h>
#include <bpf/libbpf.h>
#ifdef HAVE_LLVM_SUPPORT
#include <llvm-c/Core.h>
#include <llvm-c/Disassembler.h>
#include <llvm-c/Target.h>
#include <llvm-c/TargetMachine.h>
#endif
#ifdef HAVE_LIBBFD_SUPPORT
#include <bfd.h>
#include <dis-asm.h>
#include <tools/dis-asm-compat.h>
#endif
#include "json_writer.h"
#include "main.h"
static int oper_count;
#ifdef HAVE_LLVM_SUPPORT
#define DISASM_SPACER
typedef LLVMDisasmContextRef disasm_ctx_t;
static int printf_json(char *s)
{
s = strtok(s, " \t");
jsonw_string_field(json_wtr, "operation", s);
jsonw_name(json_wtr, "operands");
jsonw_start_array(json_wtr);
oper_count = 1;
while ((s = strtok(NULL, " \t,()")) != 0) {
jsonw_string(json_wtr, s);
oper_count++;
}
return 0;
}
/* This callback to set the ref_type is necessary to have the LLVM disassembler
* print PC-relative addresses instead of byte offsets for branch instruction
* targets.
*/
static const char *
symbol_lookup_callback(__maybe_unused void *disasm_info,
__maybe_unused uint64_t ref_value,
uint64_t *ref_type, __maybe_unused uint64_t ref_PC,
__maybe_unused const char **ref_name)
{
*ref_type = LLVMDisassembler_ReferenceType_InOut_None;
return NULL;
}
static int
init_context(disasm_ctx_t *ctx, const char *arch,
__maybe_unused const char *disassembler_options,
__maybe_unused unsigned char *image, __maybe_unused ssize_t len)
{
char *triple;
if (arch)
triple = LLVMNormalizeTargetTriple(arch);
else
triple = LLVMGetDefaultTargetTriple();
if (!triple) {
p_err("Failed to retrieve triple");
return -1;
}
*ctx = LLVMCreateDisasm(triple, NULL, 0, NULL, symbol_lookup_callback);
LLVMDisposeMessage(triple);
if (!*ctx) {
p_err("Failed to create disassembler");
return -1;
}
return 0;
}
static void destroy_context(disasm_ctx_t *ctx)
{
LLVMDisposeMessage(*ctx);
}
static int
disassemble_insn(disasm_ctx_t *ctx, unsigned char *image, ssize_t len, int pc)
{
char buf[256];
int count;
count = LLVMDisasmInstruction(*ctx, image + pc, len - pc, pc,
buf, sizeof(buf));
if (json_output)
printf_json(buf);
else
printf("%s", buf);
return count;
}
int disasm_init(void)
{
LLVMInitializeAllTargetInfos();
LLVMInitializeAllTargetMCs();
LLVMInitializeAllDisassemblers();
return 0;
}
#endif /* HAVE_LLVM_SUPPORT */
#ifdef HAVE_LIBBFD_SUPPORT
#define DISASM_SPACER "\t"
typedef struct {
struct disassemble_info *info;
disassembler_ftype disassemble;
bfd *bfdf;
} disasm_ctx_t;
static int get_exec_path(char *tpath, size_t size)
{
const char *path = "/proc/self/exe";
ssize_t len;
len = readlink(path, tpath, size - 1);
if (len <= 0)
return -1;
tpath[len] = 0;
return 0;
}
static int printf_json(void *out, const char *fmt, va_list ap)
{
char *s;
int err;
err = vasprintf(&s, fmt, ap);
if (err < 0)
return -1;
if (!oper_count) {
int i;
/* Strip trailing spaces */
i = strlen(s) - 1;
while (s[i] == ' ')
s[i--] = '\0';
jsonw_string_field(json_wtr, "operation", s);
jsonw_name(json_wtr, "operands");
jsonw_start_array(json_wtr);
oper_count++;
} else if (!strcmp(fmt, ",")) {
/* Skip */
} else {
jsonw_string(json_wtr, s);
oper_count++;
}
free(s);
return 0;
}
static int fprintf_json(void *out, const char *fmt, ...)
{
va_list ap;
int r;
va_start(ap, fmt);
r = printf_json(out, fmt, ap);
va_end(ap);
return r;
}
static int fprintf_json_styled(void *out,
enum disassembler_style style __maybe_unused,
const char *fmt, ...)
{
va_list ap;
int r;
va_start(ap, fmt);
r = printf_json(out, fmt, ap);
va_end(ap);
return r;
}
static int init_context(disasm_ctx_t *ctx, const char *arch,
const char *disassembler_options,
unsigned char *image, ssize_t len)
{
struct disassemble_info *info;
char tpath[PATH_MAX];
bfd *bfdf;
memset(tpath, 0, sizeof(tpath));
if (get_exec_path(tpath, sizeof(tpath))) {
p_err("failed to create disassembler (get_exec_path)");
return -1;
}
ctx->bfdf = bfd_openr(tpath, NULL);
if (!ctx->bfdf) {
p_err("failed to create disassembler (bfd_openr)");
return -1;
}
if (!bfd_check_format(ctx->bfdf, bfd_object)) {
p_err("failed to create disassembler (bfd_check_format)");
goto err_close;
}
bfdf = ctx->bfdf;
ctx->info = malloc(sizeof(struct disassemble_info));
if (!ctx->info) {
p_err("mem alloc failed");
goto err_close;
}
info = ctx->info;
if (json_output)
init_disassemble_info_compat(info, stdout,
(fprintf_ftype) fprintf_json,
fprintf_json_styled);
else
init_disassemble_info_compat(info, stdout,
(fprintf_ftype) fprintf,
fprintf_styled);
/* Update architecture info for offload. */
if (arch) {
const bfd_arch_info_type *inf = bfd_scan_arch(arch);
if (inf) {
bfdf->arch_info = inf;
} else {
p_err("No libbfd support for %s", arch);
goto err_free;
}
}
info->arch = bfd_get_arch(bfdf);
info->mach = bfd_get_mach(bfdf);
if (disassembler_options)
info->disassembler_options = disassembler_options;
info->buffer = image;
info->buffer_length = len;
disassemble_init_for_target(info);
#ifdef DISASM_FOUR_ARGS_SIGNATURE
ctx->disassemble = disassembler(info->arch,
bfd_big_endian(bfdf),
info->mach,
bfdf);
#else
ctx->disassemble = disassembler(bfdf);
#endif
if (!ctx->disassemble) {
p_err("failed to create disassembler");
goto err_free;
}
return 0;
err_free:
free(info);
err_close:
bfd_close(ctx->bfdf);
return -1;
}
static void destroy_context(disasm_ctx_t *ctx)
{
free(ctx->info);
bfd_close(ctx->bfdf);
}
static int
disassemble_insn(disasm_ctx_t *ctx, __maybe_unused unsigned char *image,
__maybe_unused ssize_t len, int pc)
{
return ctx->disassemble(pc, ctx->info);
}
int disasm_init(void)
{
bfd_init();
return 0;
}
#endif /* HAVE_LIBBPFD_SUPPORT */
int disasm_print_insn(unsigned char *image, ssize_t len, int opcodes,
const char *arch, const char *disassembler_options,
const struct btf *btf,
const struct bpf_prog_linfo *prog_linfo,
__u64 func_ksym, unsigned int func_idx,
bool linum)
{
const struct bpf_line_info *linfo = NULL;
unsigned int nr_skip = 0;
int count, i, pc = 0;
disasm_ctx_t ctx;
if (!len)
return -1;
if (init_context(&ctx, arch, disassembler_options, image, len))
return -1;
if (json_output)
jsonw_start_array(json_wtr);
do {
if (prog_linfo) {
linfo = bpf_prog_linfo__lfind_addr_func(prog_linfo,
func_ksym + pc,
func_idx,
nr_skip);
if (linfo)
nr_skip++;
}
if (json_output) {
jsonw_start_object(json_wtr);
oper_count = 0;
if (linfo)
btf_dump_linfo_json(btf, linfo, linum);
jsonw_name(json_wtr, "pc");
jsonw_printf(json_wtr, "\"0x%x\"", pc);
} else {
if (linfo)
btf_dump_linfo_plain(btf, linfo, "; ",
linum);
printf("%4x:" DISASM_SPACER, pc);
}
count = disassemble_insn(&ctx, image, len, pc);
if (json_output) {
/* Operand array, was started in fprintf_json. Before
* that, make sure we have a _null_ value if no operand
* other than operation code was present.
*/
if (oper_count == 1)
jsonw_null(json_wtr);
jsonw_end_array(json_wtr);
}
if (opcodes) {
if (json_output) {
jsonw_name(json_wtr, "opcodes");
jsonw_start_array(json_wtr);
for (i = 0; i < count; ++i)
jsonw_printf(json_wtr, "\"0x%02hhx\"",
(uint8_t)image[pc + i]);
jsonw_end_array(json_wtr);
} else {
printf("\n\t");
for (i = 0; i < count; ++i)
printf("%02x ",
(uint8_t)image[pc + i]);
}
}
if (json_output)
jsonw_end_object(json_wtr);
else
printf("\n");
pc += count;
} while (count > 0 && pc < len);
if (json_output)
jsonw_end_array(json_wtr);
destroy_context(&ctx);
return 0;
}
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